1. Field of the Invention
The present invention relates to a display device, and more particularly to a technique which is effectively applicable to a flexible printed circuit board for establishing an interface with an external device.
2. Description of the Related Art
A TFT (Thin Film Transistor) type liquid crystal display module which has a miniaturized liquid crystal display panel having sub pixels whose number is approximately 240×320×3 in color display has been popularly used as a display part of a portable equipment such as a mobile phone.
In general, the liquid crystal display module includes a liquid crystal display panel and a backlight which radiates light to the liquid crystal display panel, wherein in the liquid crystal display module which is used as a display part of a portable equipment such as a mobile phone, the backlight is constituted of a resin-mold frame (hereinafter referred to as a mold), a group of optical sheets and a light guide plate which are arranged in the inside of the mold, and a reflective sheet which is arranged below the light guide plate.
The liquid crystal display module for the mobile phone adopts, as a main stream, the structure in which a flexible printed circuit board which is connected with the liquid crystal display panel and establishes an interface with an external device has a portion thereof folded in a compact shape and fixed with a tape or fixed to a frame of a mold using a pressure sensitive adhesive double coated tape after being folded.
FIG. 8A and FIG. 8B are views for explaining a conventional liquid crystal display module for a mobile phone, wherein FIG. 8A is a view as viewed from above (a liquid crystal display panel side, a front face side, a viewer's side), and FIG. 8B is a view as viewed from a side surface.
The liquid crystal display panel is constituted of a pair of glass substrates (5, 6) which face each other with a liquid crystal layer sandwiched therebetween in an opposed manner, and an upper polarizer 7 and a lower polarizer (not shown in the drawing) which are adhered to the pair of glass substrates (5, 6), wherein a semiconductor chip 12 is mounted on the glass substrate 6. The liquid crystal display panel is mounted in the inside of the mold 1.
In the liquid crystal display module shown in FIG. 8A and FIG. 8B, to realize the miniaturization and the reduction in thickness, a flexible printed circuit board (hereinafter referred to as FPC) 11 is folded, and is pulled around and is fixed to a back surface side of a backlight. Further, on the FPC 11, electronic parts such as resistances and capacitors, and a white light emitting diode which constitutes a light source are mounted.
FIG. 9 is an enlarged view showing a portion A indicated by a solid line in FIG. 8B in an enlarged manner.
As shown in FIG. 9, when the liquid crystal display panel adopts the structure which pulls the FPC 11 around a back surface thereof from a terminal portion thereof with a minimum radius, as indicated by F in FIG. 9, the FPC 11 has a strong bending repulsive force (hereinafter referred to as a spring back force) and hence, the vicinity of a folded portion is fixed to the mold 1 using a pressure sensitive adhesive double coated tape 31.
As the prior art document related to the invention, a following document is named.
[Patent Document 1] JP-A-2001-318618